Various types of machinery and equipment employ, in one form or another, a belt drive system in which a belt, trained about two pulleys, serves as the means for transmitting the drive. Typically, such a drive will utilize a third pulley engaging the belt as a belt tightener to keep the belt properly adjusted so as to avoid slippage. It is commonplace to use a spring or other biasing means acting against the tightener idler to tension the belt. One of the problems with this type of drive is that the belt increases in length because of extended use, and consequently, the biasing means must be adjusted to compensate for this by repositioning of the idler. In a simple form of drive, an adjusting screw will be used to increase the biasing force and the mechanic making the adjustment may rely on "feel" as to a properly adjusted belt. It is also known to provide specifications that teach that the belt is properly adjusted when a certain amount of "give" can be detected along one run of the belt. Further, it is known to measure the amount of biasing force by a scale or the like and to indicate that a certain reading on the scale indicates proper adjustment of the drive.
All of these prior means and methods leave too much to conjecture and result in excessive belt wear, over- or under-tensioning and loss of efficiency. According to the present invention, these and other problems are solved by a simple and efficient system employing a pair of coordinated gauge means, one to indicate the position of the idler and the other to indicate the biasing force. The gauge means are so correlated that a certain reading on one gauge will indicate what reading should be attained on the other gauge, all of which is accomplished by making one adjustment which produces proper idler position according to biasing force. The readings are made easier by using identical indicia on the gauge means, preferably numerical and linear, so that when, for example, the number 2 on one gauge appears, the system is properly adjusted when the number 2 appears on the other gauge means. Further improvements are provided by arranging the components in a compact manner, easily accessible to the machine operator and occupying no unnecessary space.